Refractory organic matters (ROM) are the dominant organic matters in the membrane bioreactor -treated MSW landfill leachate, which are usually resistant to microbial degradation. Advanced membrane systems, which are expensive and generally for drinking water treatment, have to be used to make the final effluent meet discharge requirements. Anion exchange approach might be another option to remove ROM from leachate. In this study, the adsorption isotherms and kinetics were performed to illustrate the adsorption mechanism of anion exchange resins, 717 and D301R-Cl, for removing ROM from leachate. The results demonstrated that the adsorption isotherms for both resins were best represented by Langmuir model. The measured adsorption capacities of the 717 and D301-Cl resins were 39.84 and 35.84 mg COD g-1 dry resin, respectively. The adsorption kinetics of ROM onto both resins followed a pseudo-second-order model and the measured rate constants were 0.00278 and 0.00236 g mg-1 min-1 for the 717 and D301R-Cl resins, respectively. Additionally, intra-particle diffusion analysis indicated that the adsorption of ROM was controlled by both film and intra-particle diffusions. Based on the UV/Vis spectra and fluorescence EEM analysis, the UV humic-like substances were preferentially adsorbed on both resins, although more on D301R-Cl resin than 717 resin. Furthermore, column studies showed that the adsorption of ROM on both 717 and D301R-Cl resins can be divided into two phases: monolayer adsorption and multilayer adsorption, while the desorption demonstrated similar pattern but different efficiency due to the unique property of resin. The results suggested that the resins could remove ROM from leachate efficiently, while the practical progress needs to be further optimized.
Keywords: Adsorption; Anion exchange resin; Bio-treated MSW landfill leachate; Humic-like substances; Spectra analysis.
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